I'm going to raise an issue, and it could be fair to consider it a nitpick, but considering that you're trying to be rigorous, perhaps it is okay to be unusually technical.
Blue and green are not natural categories, or at least they are as natural as "sour tasting" or "stinky". To quote Bruce MacEvoy, "color is a complex judgment experienced as a sensation"; color is not an objective property of things in the world. When a human gazes at something, the color sensation they experience is highly dependent on all sorts of visual factors in the scene, and even depends on the memory and expectation of the human.
When I say, "that object is red", I mean it as shorthand for "that object has a reflectance, transmittance, and emittance profile that usually leads humans to experience a red color sensation when viewing the object in neutral-ish conditions". And let it be known that "red color sensation" and "neutral-ish conditions" are still massive shorthand. So really, "that object is red" is a statement concerning 1) the object 2) the human visual system 3) qualia 4) common viewing environments for humans.
I point this out because it seems wrong to try to do a bunch of rigorous thinking founded upon an extremely flawed example (flawed in the example is supposed to be about objective things, but is actually about subjective things). We even have Eliezer Yudkowsky talking about the nature of truth and using statements like "snow is white if and only if snow is white". It might sound like he's talking about facts, but imagine the analogous sentence "skunks are stinky if and only if skunks are stinky" or "chess is interesting if and only if chess is interesting". Now it is more clear the statement is about subjective experiences and actually fails to have a definite truth value.
Would you be comfortable if your natural category example was whether some music was soothing, or whether some object was bitter? If you would not be comfortable with using those subjective examples, you should not be comfortable using color as an example. If you are comfortable with those examples, you can disregard the issue I raise.
I think a lot of your points still stand, but you're taking unnecessary risks by using a flawed example.
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You could mean that.
Or you could mean it as shorthand for "that object emits or reflects electromagnetic radiation with a pronounced peak around 700nm wavelength".
Neat, I recognize your username. I always liked your choice of username, and I've often enjoyed your comments. Thanks.
Except that is not sufficient nor necessary to ensure that the object would typically generate a red color sensation in humans, even in "neutral or typical conditions". So, I would not mean it as shorthand for that. Color sensations can not be boiled down to or predicted by spectral power distributions and reflectance profiles only.
I'm thinking your comment perhaps was a gentle nudge to say, "it's not too hard to make color an objective creature". Well, you can come up with some objective definition of whether some object has the property of redness, but you'd have to basically reimplement the human visual system and assume a huge amount about the object's current surroundings (or you could not go to that effort and end up with something that does a very poor job of corresponding to human color sensations). It would be similar to converting bitterness of food or soothingness of music into objective properties. Or maybe your comment was a gentle nudge in a completely different direction.